Spherical (Slerp) Activation Rotation Steering

Steers a hidden activation by treating its normalized direction as a point on the unit hypersphere and moving it along the shortest geodesic (spherical linear interpolation, Slerp) toward a diff-in-means-derived target direction, then rescaling back to the original norm — a norm-preserving alternative to additive steering (CAA/ITI), with a von Mises-Fisher-based confidence gate setting the per-token rotation amount from the activation's own angular alignment.